Glacial Lake development and marine inundation,Deer Lake area,Newfoundland, Canada: Topographically controlled deglaciation of an interior Basin

A large interior basin in west-central Newfoundland (covering the area of modern Deer Lake, Grand Lake, Sandy Lake and Birchy Lake) is connected to the sea by a narrow breach of a coastal mountain range. During retreat of Late Wisconsinan glaciers, this basin was occupied by a short-lived glacial lake impounded by remnant ice in coastal fjords, and drained by a spillway at the western end of the lake. Evidence for this lake is fragmentary, and consists of strandline features that fall on a plane of elevation consistent with the post-glacial isostatic tilt. Following collapse of the ice dams and subsequent lake drainage at some time prior to 12 220 yr BP, the Deer Lake basin was inundated by the sea to an elevation of about 45 m a.s.l. Deltas were formed at the basin edges, and thick successions of fine-grained rhythmites blanketed the basin floor. Isostatic rebound resulted in falling relative sea levels, and, following a stillstand marked by a period of deltaic deposition at 33 m a.s.l., isolation of the Deer Lake basin from marine influence in the early Holocene. This style of deglaciation differs from previously accepted models for this part of eastern Canada, which showed progressive retreat from the coast to remnant centres on topographic highs. In the model proposed here, a large, low-elevation basin was deglaciated early, at a similar time to ice retreat to coastal positions from offshore. This pattern of deglaciation may be found in other areas with similar topographic settings.